(1) Field of the Invention
The present invention relates to the cutting of sheet material and particularly to the trimming of stacked paper sheets such as, for example, in the manufacture of books. More specifically, the present invention is directed to a three-cutter guillotine for trimming sheet material by cutting along three sides of such material. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
(2) Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well suited for use in the manufacture of books. It is often necessary, in the course of the manufacture of a book, to trim the inner book to size by effecting cuts along three sides which are respectively known in the trade as the "head", "foot", "front" sides. Apparatus for performing this trimming is known as a guillotine. Guillotines employing three cutting blades or knives are known. In such prior art three-cutter guillotines, the work is automatically guided beneath the cutters, aligned and maintained on a cutting table by means of a press ram and the head and foot trimming occurs in a first work stroke. Subsequently, the front trimming is effected in a second work stroke. The work is thereafter automatically ejected from the guillotine and placed on a conveyor belt.
The prior art three-cutter guillotines, as briefly described above, perform trimming cuts which are spaced in time; i.e., the front trimming is not performed until the head and foot trimming has been completed and the cutter blades employed therein fully retracted. Accordingly, previously available three-cutter guillotines have been severely restricted in operating speed to the extent that such apparatus cannot be integrated into presentday high capacity production lines.
In an effort to overcome the above-discussed problem of slow operating speed of three-cutter guillotines, two-station flow cutters have been proposed wherein trimming is accomplished at two successive cutting stations. Specifically, the head and foot trimming are executed in a first station and the front side trimming will occur at a subsequent second station. Pressing, transfer from the first to the second station and feed and discharge all occur automatically. While an enhanced operational speed has been achieved with two-station flow cutters as compared to prior three-cutter guillotines, an increase in manufacturing capacity has not been realized for a number of reasons. Firstly, the height of the stack to be cut is limited due to the transport between cutting stations. Secondly, the precision with which the cuts are made has suffered as a result of the added handling of the work. It is also to be noted that two-station flow cutters are quite costly, due to their structural complexity, and are generally considered as requiring an excessive amount of floor space.